1. Field of the Invention
The present invention is related to a wafer tester for a photo sensor, and particularly to a wafer tester that includes a heat-resistant lens kit to form an enclosed room for isolating the surface of a device under test.
2. Description of the Related Art
It is necessary for a CMOS sensor to be tested under low-temperature environment for sure of practical work in the low-temperature environment.
FIG. 1 is a schematic diagram of a wafer tester 10 having a test base 11 as an upper portion and a chuck 13 for loading a device under test as a bottom portion. The test base 11 includes a pogo tower 13, a probe card 14 and a test head 16. The test head 16 is associated with a test probe 18 for touching a device under test, a room for light transmission and a probe card holder 17 for connecting the pogo tower 12 and the probe card 14 into a piece. Obviously, there is a hole individually in the pogo tower 12, probe card 14 and a test head 16 for passing light onto the device under test. Shown in FIG. 1, in order to maintain a device in a low-temperature state, the device under test is necessarily attached to the chuck 13 through low-temperature treatment for sure of low temperature. Meanwhile, the probe card 14 of the wafer tester 10 is close to the device under test in low-temperature state. However, the device under test is in low-temperature state on one hand. On the other hand, the probe card 14 is in room-temperature or higher-temperature state. Thus, there is vapor, also called as saturated vapor, formed on the interface of the low-temperature surface and the high-temperature surface. When light is incident continuously, light though vapor may be reflected, refracted or scattered. Thus, light incident on the device under test may be disordered and further cause incorrect measurement and short to damage the apparatus. Thus, in order to correctly and rapidly test the device under test, the vapor generation should be overcome.